package Problem;


import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

public class TreeNode {
      int val;
      TreeNode left;
      TreeNode right;
      TreeNode() {}
      TreeNode(int val) { this.val = val; }
      TreeNode(int val, TreeNode left, TreeNode right) {
          this.val = val;
          this.left = left;
          this.right = right;
      }
  }

class Solution {
    public List<List<Integer>> levelOrder(TreeNode root) {
        List<List<Integer>> list = new ArrayList<>();
        Queue<TreeNode> queue = new LinkedList();
        queue.offer(root);
        while(!queue.isEmpty()) {
            int size = queue.size();
            List<Integer> list1 = new ArrayList<>();
            for(int i = 0;i < size ; i++) {
                TreeNode poll = queue.poll();
                if(poll.left != null) {
                    queue.offer(poll.left);
                }else if(poll.right != null) {
                    queue.offer(poll.right);
                }
                list1.add(poll.val);
            }
            list.add(list1);
        }
        return list;

    }
}
